1. Field of the Invention
The present invention relates to a sheet aligning apparatus for aligning sheets, and more particularly, it relates to a sheet aligning apparatus for aligning stacked sheets to form an aligned sheet bundle to be conveyed to a bookbinding apparatus, and a bookbinding apparatus having such a sheet aligning apparatus.
2. Related Background Art
In the past, a plurality of sheet aligning apparatuses were provided so that sheets are introduced into one of the sheet aligning apparatus while a sheet bundle is being discharged from the other sheet aligning apparatus. In this way, by using the sheet aligning apparatuses alternately, the continuous sheet supply was permitted.
Further, as shown in FIGS. 18A and 18B, there has been proposed a sheet aligning apparatus having stop fingers 305 acting as a temporary shorting means. In this aligning apparatus, each of the stop fingers 305 is formed from a plate member having an L-shaped cross-section and includes a sheet abutment portion 305a and a bottom portion or sheet dip portion 305b. Further, each stop finger is fixedly mounted on a drive shaft 305c so that the stop finger can selectively be shifted between a storing position where a sheet is guided to the dip portion 305b to abut the sheet against the abutment portion 305a and a retract position where the dip portion is spaced apart from a sheet convey surface. In addition, the stop fingers can be rotated from the storing position in an anti-clockwise direction to discharge the sheets stored on the stop fingers 305 onto a containing tray.
Incidentally, in FIGS. 18A and 18B, the reference numeral 306 denotes a paddle (sheet aligning means which can be rotated to afford an advancing force to the sheet, thereby aligning the sheet in a sheet conveying direction; 307 denotes an aligning means for aligning the sheets (sheet bundle) in a width-wise direction of the sheet and having a fixed reference plate 307a and a movable plate 307b shiftable in directions shown by the double-headed arrow to align the sheets; 309a and 309b denote sheet tip end abutment members shiftable between a protruded position where a tip end of the sheet abuts against the abutment members and a retract position where the sheet or the sheet bundle is not prevented from being conveyed from the containing tray; 310 denotes the above-mentioned containing tray; 311a, 311b and 311c denote inlet sheet upper guides; 313 denotes an inlet sheet lower guide; and 339 denotes a pair of convey rollers for conveying the sheet or the sheet bundle into the aligning apparatus.
The sheets successively conveyed into the aligning apparatus by means of the pair of convey rollers 339 are supplied onto the containing tray 310 while being guided by the inlet sheet upper guides 311a, 311b, 311c and the inlet sheet lower guide 313 in the vicinity of a sheet inlet, and then are urged against the fixed reference plate 307a and the tip end abutment members 309a, 309b by the movements of the sheet aligning means 306 and the movable plate 307b of the aligning means 307, thereby aligning the sheets.
The sheet bundle aligned by the sheet aligning apparatus is conveyed, by the convey means, from the containing tray 310 to a sheet post-treatment means for performing post-treatment (for example, stapling). In this case, the tip end abutment members 309a, 309b are shifted to the retract position so as not to interfere with the conveyance of the sheet bundle, and tip ends of the dip portions 305 of the stop fingers 305 are urged against an upper surface of the sheet bundle to be conveyed. In this condition, the next sheets (for a next sheet bundle) conveyed from the pair of convey rollers 339 are guided by the dip portions 305b of the stop fingers 305 and are urged against the abutment portions 305a, thereby storing the next sheets. After the previously aligned sheet bundle was conveyed by the convey means, the tip end abutment members 309a, 309b are returned to the protruded position, and, at the same time, the stop fingers 305 are rotated in the anti-clockwise direction by the drive shaft 305c, thereby dropping the next sheet bundle temporarily stored on the stop fingers 305 onto the containing tray 310.
However, in the above-mentioned conventional technique, after the sheets are stored temporarily by the stop fingers 305, when the sheets are transferred to the containing tray 310 by the rotation of the stop fingers 305, since the sheets are freely dropped from the stop fingers 305, if any air enters between the sheets during the dropping of the sheets onto the containing tray, the aligned sheets may be disordered. Although the disorder of an uppermost sheet can be corrected by abutting the uppermost sheet against the tip end abutment members 309a, 309b by the rotation of the aligning paddle 306 and the lateral disorder of the sheet bundle can be corrected by abutting the sheet bundle against the fixed reference plate 307a by the movement of the movable plate 307b, the other disordered conditions cannot be corrected in the above-mentioned sheet aligning apparatus. Thus, if the sheet bundle is conveyed to the stapling means (post-treatment means) in the disordered condition, the poor bookbinding will occur.
Further, since the stop fingers 305 are rotated around the drive shaft 305c, in dependence upon a thickness of a single sheet bundle, an angle between the top surface of the sheet bundle and the dip portions 305b of the stop fingers 305 is varied, with the result that a gap is created between the dip portions 305b and the sheet bundle, which may lead to incorrect storing of the next sheets. To avoid this, it is considered that various kinds of stop fingers are prepared and the stop fingers are changed in accordance with the thickness of the sheet bundle. However, in this method, the operation for replacing the stop fingers is troublesome, and since various kinds of stop fingers must always be prepared, the entire apparatus is made to be more expensive.